Method of and means for balancing telegraph lines



Oct. 13, 1931. I A, F CQNNERY ET AL 1,826,737

METHOD OF AND MEANS FOR BALANCING TELEGRAPH LINES Filed Aug. '8, 1930INVENTOR ALDER E CONNERY RONALD $.WISHART Patented Oct; '1 11 931systems and more particularly to' a system for UNITED-'1[STATES PAT ToFFlcE ALDER F. coNNER F nnooxnvmnivn RONALD s. wIsHAmyon ROCKVI IQLECENTER. 7

NEW YORK, ASSIGNORS TO INTERNATIONAL COMMUNICATIONS LABORATORIES, I I

INC on NEW YORK, N. Y., A- CORPORATION 'oF NEW'YORK METHOD on AND;MEAlNgFOR BALANonve TELE RAPH 'Lmns' I i Application fi1efl.- Ang| 1st8,'1930. s n n 473,384; f

.This invention relates-to communication determining the degree ofbalance between a line and an artificial line.

13' As is'well known in the art'; a balance must be maintainedbetween areal line and an a rtificial line in order that reception ofsignals:

over a. duplex telegraph circuit maybe undisturbed. The artificiallineis made up of a plurality of variable resistances to balance theresistance of the line'and a plurality of variableconden'sers withvariable resistances in series with them, to balance the capacity of theline; There also may bein the artificial line one or more fixedcondensers with or without resistances inseries with them. In 1 somecases there may" be; either 'afixed or variable inductance inserted inthe artificial line. The artificial line is thus constructedto containwithinits limits of variation some combination of resistance, timedcapacity and inductancewhich will closely sim'ulate the artificialline15 which-is'composed'of vari-' real line which it is to balance.v 1 VThe real or mainline conditions varywlth weather: and changes in wires;'Inorder to keep the artificial line and realline in a'state state ofbalancesome means must be provided amount of resistance unbalance. Inaddicate the capacity unbalance betweenfthe' two.

Under certain conditions the effect oflump inductances'in the linevaries due to leakage to ground along a conductor. This-condition makesit diflicu'lt to obtain a true capacity balance. In order to overcomethis feature it.- has been found possible to match the induc tance'in'the real line with avariable. induce tanc'e inthe artificialline.

1 Ina copending application SerialNo.

228 filed Julyl, 1930 by us is describeda new method of ascertaining, acapacity un balance by using a meter; responsive to A.

C. current which indicates the induction on :the line and the degreeuofcapacity 'unbal tractile sprlng.

ance. Under conditions in which there is a large amount of inductance inthe'line obtain a correct capacltyglunj is difficult to ba an It is,therefore, the principal objectof this invention to provlde-vmeanswhereby-the inductance ofthe" real line may be matched thereof; 1

.be had from the following descriptiom',

taken in conj unction with the accompanying drawings in which 1 liigure1 discloses the-circuit employing the invention; T T J y 1? 1g. 2 is aseries iofgraphs showing the relation of the currentsinan unbalancedsystem.

Fig. 1 discloses a station l0 connectedtoa llne or cable 2 A polarizedline relay3 is connected to the real line Qthrou'gh one of Its wlndingsand thence to winding i of a differential C(millianimeterfi: The windlng6 of the mil'lia n'meter 1 is connected through the other winding ofrelay 3- tothe able condensers 8, variable resistances 7, a"

inductance 18. The apex of meter 5 is-conne'ctedto atwo-p'ointswitch 11;one point:

A. C. current of a frequencywithin the signal range of the line. It maybe a'specially pro- I vlcled-commutator or it may be'a portion of" theusualdistributor. v

the line"2ja'nd the {artificial-line 15. It has not beenthought-necessary 'to' disclose the sitioned between two laminated polepieces. Secured to the armature is a pointerwhich is'maintained in azeroposition by are The condenser l6 'is provided to prevent the flow ofdirect current through themeter 14 while balancing, and eliminates theneceslarge variable resistance 17 and a variable highly air-dampedgalvanometer is bridged in series with a condenser16 across:

sity of having the distant station ground the line while a balance isbeing taken. The value of the capacity is such thatin conjunction withthe inductanceand resistance ofthe, 5 meter, A; O. frequencies from zero,to 450 cycles willnot be seriously impeded.

The use of the A. C. commutator 9 having a frequency prefer range setsupa condition which-assimilates 10 actual signaling conditions and the-A-. C.

meter indicates the difference between the value and phase r inductivelriclrs in the artificial line and the. main line, thereby indicatingthe degree of unbalance.

The procedure in balancin-gea circuit'is to, 7, move theswitch 1:1 tothe left and the key 12. is slowly operatedJ-and resistance 17 v isradjusted until the needle of meter 5 gives,

20 equal readings with the-key open and closed. This is called. 'aresistance balance and is well known inthe art, 1 i a A readingis no wtakenionthe A. G. bah,

finance indicator 14 and note isma-deeof; the del 2 fiection which isdue'totheinduction in the main line. Assuming that the scale ofthis,meter is calibrated from O to 20 milliamperes intwo milliamperesdivisions, the reading,

itdue to induction may be assumed to be from 39 4c to 6 millia-mperesp vThe switchllzis now moved to the right and the commutator 9 is startedand aread-- ing is againtaken on-indicator 14;,which isan; indicationofunbalanceidue to capacity,

plus the =amount-of induction. This :may be 18 milliamperes; tCondensersfi and retarda-g tion resistances 7- are now; adjusted; untilthe indicatonreads between .4 zand tiat which point-the line is in astate of balance. 1;; i

It is sometimes found that the balancecan i not be reduced to thevalueof the-induction 4 and '6; and that thebest possible balance is. severalmilliamperes above; the induction value. Thisisduertothe eifectof; theimpedjancelof the windings of the distantterminal, duplex relays, themargin ofunloalance being greatenthelarger the impedance. T his; isalso. sometimes due to lump =inducta-ncesoccurring in the linewireqitself cas; in the 1 case of intermediate composite telephoneequipment:

In the above descriptiomthe; frequency of the A; C; applied to the;split of the duplex;

I has been stated as preferably withinithe signaling range of thecircuit. (hen induc tance-exists toa noticeable extent in the com-tmunication circuit," and if: not compensated for or matched intheartificial .lin e,, a'balance obtained with an A. C; frequency equat tothe maximum frequency ofoperation of the circuit may not be satisfactoryfor the; lower frequencies, and vice-'versat Aerelation of-frequenciesin operation may, befro n five to thirty-cycles per second, forinstanceIf the inductance on the line is low and the elation of'the capacityandvltigiyesa reading as near the induc as possible.

' conditionof balance D represents ment of timing 1 resistances.

variable timing resistances are manipulated, the indicator of meter 14Lwill very nearly approach the induction reading which was noted, namely,from l to ,6, milliamperes, If, however, the inductance of the line isvery high the resistances and condensers may be ad usted until the meterreads, ably within the signaling for example,

of-the--condensers will cause theineedletto move up-ag-ai-n, indicatingthat the inductance is high, I p

At this point the variable inductance 18 may, be, adjusted to match theinductance in the real line. This is done by first adjusting the;variable inductance 1 8 and; then the irelOinill-iampe-res. Anyfurthermanipulation sistancesf? and condensers; 8 unti l the me er Fig,2, ,discloses a series 10f, bscillograms in whichA indicates theinduction in a certaialine, B acon i i n, n al nce another. us to wrongadjust-I eltwill be noted that C does-not efgactlyduplicate This duejtothe fact thatit is almost impossible to obtain an absolutely perfectbalance,

Graph indicates the efiect on a b 'n a linetcaused by a certain.

of inductance 1 77 type ofte 'm nal relay. Graph? indicates condition ofunbalance d Lthe-eifect of anothentype of terminal relay.

Itwill be seen from these graphsthat highg inductancewill reat aifectthe curve C to;

- such anextent that itg will be impossibleto;

.match the inductance in the: realgline, the

disturbance-An ;E .will,ap,proach E k and a more perfect balance maybeobtained t lt-isuobvioii ir m the fO g i described, but; can ,be usedvin conjunction with other types o networks.

Whatisclaimed isa l.-';I;n;a telegraph system, areal 'line, anrartifical ne; con a ning a Variable indlw tance, a; polarized a relay, adii l'erentiall ll CY. millia-nimeter connected to saidlines throughsaid, relay-and to; a two-point switch, a key 1 connected to one of t epoints ofsaid switch,

7 hat the} '3 method o t i eds set mlte ts usete. obtaining abalance, onthe forms of network tionvalue and Ca.

alance isms a ,3

of capacity unbalance therein, and thencorrecting said capacityunbalance-by Varying the inductance and capacity in said artifica-lline. i I

5 i 3. In a communication system, a method of balancing tWoYlinescomprising alternately impressing current of opposite polarity on saidlines, taking a reading of resistance unbalance therebetween, adjustingthe resist-,

ance in one of said lines until a resistance balance is obtained, takinga' reading of'the induction in said lines, impressing alternatingcurrent on saidlines of a frequency within the signaling range, taking asecondireading indicating the induction and capacity un-' balance,adjusting the line to eliminate the capacity unbalance, and Varying'theinductance in one of said lines until the induction 1 and capacityreading approximates the induction reading. p a v 4:- In a communicationsystem, the method of eliminating a state of capacityunbalance between areal line and its artificial line,: said artificial line having Variablecapacity and inductance therein, comprising taking a,

reading indicating the induction on said real v s line, impressingalternating current on said lines of a frequency Within the signalingrange, taking a second reading indicating the inductance and capacityunbalance, and then.

adjusting the capacity and inductance to approximate said first reading.

5. In a telegraph system, a method of eliminating a state of unbalancebetween a real line and its artificial line consisting in ascertainingthe resistance unbalance, correcting such unbalance, ascertaining theinductionon the line, impressing alternating current of a'frequencyWithin the signaling range on 40 said lines, to ascertain the state ofcapacity unbalance therein, and'then correcting said capacity unbalanceby varying the inductance and capacity in said artificial line. a I 1 InWitness whereof, We hereunto-subscribe;

our names this 4th day of'August, 1930.

' v ALDER F. CONNERY. RONALD S. WISHART.

